Modern straight cylindrical dental burs are generally exemplified by a design which incorporates both side and end cutting surfaces, with each cutting surface respectively having about six teeth. The most generally acceptable side tooth configuration for a cylindrical dental bur, due to the inherent self-cleaning characteristics, is that of a helix curve, wherein each such tooth is machined by grinding into the working stock of a blank bur head workpiece by two series of six successive grinding disk cuts. The first series of side tooth helical grinding cuts form six equal size abutting ogee configured grooves about the longitudinal circumference of the blank bur head workpiece and it is that series of grinding cut operations which removes the greatest amount of bur head workpiece material, as well as consuming the greatest amount of machining time. The second series of side tooth grinding disk cuts successively follows the respective groove traces formed by the first series of cuts, but is accomplished with a profiled grinding disk which forms relief surface cutting edges along the trace of each longitudinal circumferential groove cut. Lastly, a series of six separate grinding disk end cuts are made to form face teeth on the working end surface of the dental bur. Thus, it requires a total of three separate grinding disk cuts to complete each set of finished side and face teeth on a straight cylindrical dental bur of the type described, i.e., in the grinding of a straight cylindrical helically configured six side-and-face toothed bur, it requires a total of eighteen cuts by grinding disks when making a bur having the aforementioned exemplary six teeth.
The equipment which has been historically employed, as well as also that which is presently available, for grinding the aforementioned types of dental burs is generally comprised of single station grinding machines which are manually loaded and unloaded with a single blank bur head workpiece at a time, and then activated to cycle through a separate non-concurrent sequence of successive grinding and indexing operations to produce a finished dental bur in accordance with the sequential machining process heretofore described. Additionally, in the grindable machining of dental burs, it has been the custom to employ relatively small diameter grinding disks, in the size range of 2-inches or so, on the bur grinding machines heretofore and presently known -- being also a factor of consequence in determining overall productive capacity of said machines in that the corresponding relatively short circumferential cutting surface of such small diameter disks wear down rapidly when subjected to grindably machining the relatively hard blank bur head workpiece materials currently in use, thereby necessitating frequent replacement of worn grinding disks with new or re-dressed grinding disks, thus resulting in frequent periods of non-productive downtime for purposes of grinding disk replacement.
Progress in improving dental bur grinding machines has been slow in coming, a consequence contributed to by the attitude of secrecy which has likewise historically characterized the industry. However, machine developments made in the grinding of twist drills, an area of art similar to that of grinding dental burs, sets forth certain teachings in the automation of grinding operations. Examples of automated twist drill grinding disclosures are such as those shown and taught in U.S. Pat. No. 978,097 to Wilt, Jr., dated Dec. 6, 1910; U.S. Pat. No. 2,850,849 to Babbitt, dated Sept. 9, 1958; and U.S. Pat. No. 3,309,819 to Guhring, dated Mar. 21, 1967. The aforementioned disclosures, although they may in certain respects show machines which are somewhat structurally and functionally similar to the present invention, said disclosures are, nonetheless, mechanically, as well as operationally and patentably, distinguishable from the present invention.
The present invention pertains to a machine designed for the high-speed automated production of precision dental burs. The limiting features and shortcomings of the prior art and the collateral prior art referred to above are obviated in the design of the machine comprising the present invention, and a substantial number of improvements in the art of forming modern dental burs are provided by the machine of the present invention, details of which are set forth in the following specification and illustrated in the accompanying drawings comprising a part thereof.